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The First Direct Evidence of a Late Devonian Coelacanth Fish Feeding on Conodont Animals

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The First Direct Evidence of a Late Devonian Coelacanth Fish Feeding on Conodont Animals Sci Nat (2017) 104: 26 DOI 10.1007/s00114-017-1455-7 SHORT COMMUNICATION The first direct evidence of a Late Devonian coelacanth fish feeding on conodont animals Michał Zatoń1 & Krzysztof Broda1 & Martin Qvarnström2 & Grzegorz Niedźwiedzki2 & Per Erik Ahlberg2 Received: 9 February 2017 /Revised: 28 February 2017 /Accepted: 2 March 2017 /Published online: 10 March 2017 # The Author(s) 2017. This article is published with open access at Springerlink.com Abstract We describe the first known occurrence of a Introduction Devonian coelacanth specimen from the lower Famennian of the Holy Cross Mountains, Poland, with a conodont Coelacanths are sarcopterygian fishes which have a long evo- element preserved in its digestive tract. A small spiral lutionary history ranging back to the Early Devonian (Zhu and phosphatic coprolite (fossil excrement) containing et al. 2012). The group comprised numerous species in numerous conodont elements and other unrecognized re- the geological past, but today is represented by the single mains was also found in the same deposits. The coprolite genus Latimeria, first discovered in 1938 in the Indian is tentatively attributed to the coelacanth. Although it is Ocean. Although the extant Latimeria occupies a deep-sea unclear whether the Late Devonian coelacanth from habitat, fossil coelacanths inhabited a range of different Poland was an active predator or a scavenger, these finds palaeoenvironments and evidently occupied various ecologi- provide the first direct evidence of feeding on conodont cal niches, as indicated by their occurrence in different facies animals by early coelacanth fish, and one of the few and their morphological disparity (Friedman and Coates 2006; evidences of feeding on these animals known to date. It Wendruff and Wilson 2012). Despite growing knowledge also expands our knowledge about the diet and trophic about fossil coelacanth diversity, disparity, anatomy, and even relations between the Paleozoic marine animals in ontogeny (Wendruff and Wilson 2012; Gess and Coates general. 2015), there is still insufficient data on some important palaeobiological aspects, including diets. Gut contents are an important source of direct evidence on food gathering by fos- Keywords Coelacanth . Conodonts . Gut content . sil organisms, including fishes. These, however, are extremely Coprolite . Devonian rare in fossil coelacanths. To date, recognizable gut contents have been recorded in only two species. Lund and Lund (1984, 1985) found scales and even an intact paleostomatopod shrimp in the species Caridosuctor Communicated by: Sven Thatje populosum from the Lower Carboniferous Bear Gulch Limestone of MT, USA. Clement (2005)foundaganoidscale, Electronic supplementary material The online version of this article (doi:10.1007/s00114-017-1455-7) contains supplementary material, arthropod appendages, and a crushed, incomplete crustacean which is available to authorized users. within the body cavity of Wenzia latimerae from the Upper Jurassic of France. Recently, Yabumoto and Brito (2013)re- * Michał Zatoń ported some unrecognizable stomach contents in the [email protected] mawsoniid coelacanth Axelrodichthys araripensis from the Lower Cretaceous Crato Formation of Brazil. 1 Faculty of Earth Sciences, University of Silesia, Będzińska 60, In the present paper, we report the presence of a single 41-200 Sosnowiec, Poland conodont element from the gut content of a coelacanth spec- 2 – Department of Organismal Biology, Uppsala University, imen (Fig. 1a b) from the Upper Devonian deposits of Norbyvägen 18A, 752 36 Uppsala, Sweden Poland. Additionally, several conodont elements have also 26 Page 2 of 5 Sci Nat (2017) 104: 26 Fig. 1 a Coelacanth fish, specimen GIUS 4–3654/1. b Conodont organization of this specimen. h head, op opercula, tf tail fin. Scale bars element found in its digestive tract. c Conodont-bearing, spiral coprolite 10 mm (a), 0.2 mm (b), and 3 mm (c–d) specimen GIUS 4–3624/4. d Virtual thin section showing spiral internal been detected within a phosphatic and spiral coprolite found in Results the same deposits (Fig. 1c–d). The gut content, and possibly the coprolite, is the first direct evidence for feeding on cono- The coelacanth found in the lower Famennian deposits is not dont animals by Late Devonian coelacanth fishes. well-preserved, but represents an articulated skeleton consisting of part and counterpart. The general characteristics of the skeleton, especially the morphology of the gular plates and opercula, suggest that the coelacanth may represent, or be Material and methods closely related to, the genus Diplocercides, of which isolated remains are known from other Famennian localities in the The coelacanth fish and conodont-bearing coprolite were Holy Cross Mountains (Szrek 2007). However, a more precise found in the Upper Devonian (lower Famennian) marly identification is difficult due to the poor preservation of the shales outcropping in the Kowala quarry, Holy Cross cranial skeleton. The length of the specimen is 15 cm from the Mountains, Poland. These deposits are already known to tip of its snout to the posterior end of its caudal fin. The yield abundant phosphatized arthropod cuticles and copro- conodont element has been found embedded within a light- lites (Zatoń et al. 2014;Zatoń and Rakociński 2014). Both brown phosphatic mass occurring in the posterior part of the the coelacanth fossil and the spiral coprolite were exam- coelacanth (Fig. 1a). The conodont is represented by a plat- ined uncoated and under low vacuum condition using a form element most likely representing the polygnathid genus Philips XL30 environmental scanning electron microscope Ctenopolygnathus. It is 1.5 mm long and its surface is well- (ESEM). Both the stomach content and the coprolite fossil preserved, lacking any signs of etching caused by digestive inclusions (that were visible on the exterior) were docu- processes (Fig. 1b). mented using back-scattered electron (BSE) imaging. Synchrotron microtomography showed that the spiral cop- Additionally, in order to retrieve high-resolution, three- rolite (Fig. 1c–d)containsnumerousconodontinclusions,in- dimensional data from both the coprolite’sexteriorand cluding four pectiniform elements and many isolated interior, it was scanned using propagation phase-contrast coniform elements (Fig. 2b, e). The recognizable Pa-element synchrotron microtomography (PPC-SRμCT) at beamline is similar to the species Mehlina kielcensis (Fig. 2f). The co- ID19 of the European Synchrotron Radiation Facility nodont inclusions occur in a dense coprolite matrix (Fig. 2a, (ESRF), France (Supplementary info). c–d) which in part probably represent other digested parts of The specimens are housed at the Faculty of Earth the conodont jaw apparatus or digested biomineralized struc- Sciences, University of Silesia, Sosnowiec, Poland, ab- tures. Additionally, elongated, less dense structures with breviated GIUS 4-3654/1 (coelacanth) and GIUS 4- etched extremities occur in association with the conodont 3624/4 (coprolite). teeth (Fig. 2d). It is possible that these elements also originate Sci Nat (2017) 104: 26 Page 3 of 5 26 Fig. 2 Conodont tooth elements found in the scanned coprolite. a Virtual pectiniform element (white arrow), and elongated enigmatic structures of thin section showing one pectiniform and several coniform conodont possible conodont origin (long arrows). e Segmented conodont tooth tooth elements (white arrows). b Segmented conodont tooth elements, elements and dense coprolite matrix, probably representing digested where the lowest specimen is the same pectiniform element as shown in a. biomineralized tissues. f Polygnathid conodont element similar to c Virtual thin section showing biomineralized structures and conodont Mehlina kielcensis. co coprolite mass, hs host sediment, a air. Scale tooth element (white arrow). d A virtual thin section of the coprolite bars 0.6 mm (a), 0.2 mm (bi), 0.15 mm (bii, biii), 0.5 mm (c), 0.85 mm showing dense accumulation of digested biomineralized structures, one (d), 0.25 mm (e), and 0.05 mm (f) from the jaw apparatus or other parts of the conodont animal, (Oulodus and Icriodus), have been found within the gut region but poor preservation rules out more precise identification. of a palaeoniscoid fish from the Upper Devonian Gogo Another coprolite (9.5 mm long and 8.3 mm wide) found in Formation in Australia by Nicoll (1977). In the same formation, the same lower Famennian deposits at the Kowala quarry has Choo et al. (2009) found a basal actinopterygian fish previously been shown using ESEM to contain a single cono- Gogosardina with prioniodinid conodont elements preserved dont element embedded within a phosphatic fecal mass (Zatoń in its branchial regions. Williams (1990) noted conodont ele- and Rakociński 2014). ments inside 9% of all specimens of Cladoselache sharks from the Famennian Cleveland Shale of Ohio. Conodont elements have also been found within the enigmatic metazoan called Discussion Typhloesus wellsi from the Carboniferous Bear Gulch Limestone in Montana (Conway Morris 1990). The presence of a conodont element within the Famennian Thus, the find not only supports the earlier notions that coelacanth is not the result of any post-mortem process, as it conodont animals, the extinct chordates (Purnell et al. 1995) is clearly embedded within the phosphatic mass occurring be- which were particularly abundant in the Late Devonian seas tween the part and counterpart of the preserved fish. Therefore, (Dzik 2002), were
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